Cyclic safety control for burners and the like



3 Sheets-Sheet 1 G. D. BOWER Filed Nov. 22, 1940 CYCLIC SAFETY CONTROLFOR BURNERS AND THE LIKE Q /1/ P/EKNUSTAT March 25, 1947.

March 25, 1947. QW 2,417,909

cYcLIc SAFETY CONTROL FOR BURNERS AND THE LIKE Filed'Nov. 22, 1940 3Sheets-Sheet 2 lM/E/W'an: I 660176: 0. learn,

lrfbnun s.

Patented Mar. 25, 1947 CYCLIC SAFETY CONTROL FOB BUBNERS ANDTHE GeorgeD. Bower, Universityflity, Mm, assignato Automatic Control Corporation,St. Louis, Mo., a corporation of Delaware Application November 22, 1940,Serial No. 366,512

28 Claims. (01. 158-28)- This invention relates to a control for aheatchange device, particularly a burner such as an oil or a gasfurnace, but capable in whole or in part of more general application.

The mechanism includes generally. a device subject to movement uponchange of heat, a space or room thermostat, a relay, here operated witha transformer in connection with the space thermostat, a timing orcontrol motonand a series of cam-operated switches controlled by'thetiming motor. The mechanism is used with an ignition device and a fuelsupply device or air supply device, or both, generally designated aburner motoror burner operating device.

The mechanism provides a starting period, a running period and ascavenging period. In normal operation, upon demand by the spacethermostat a starting period is instituted, by an instituting circuitclosed for a limited interval. After it is established it becomesindependent of the room thermostat. It includes a first phase at the endof which, absent ignition; lock-out occurs, and a second phase. at theend of which, with ignition, a running period is established, dependentupon the room thermostat, if starting was effective. Upon satisfactionof the room thermostat, the running period yields to a scavengingperiod, at the end of which the mechanism stops prepared for a newoperation.

If ignition is not efiective at the beginning and during the secondphase of the starting period, the mechanism assumes a lock-out position,as noted, requiring manual reset. Such manual reset establishes thescavenging period at the end of which the mechanism tries once again tostart.

If ignition failsduring the running period, the scavenging period isestablished, at the end of which the mechanism may attempt to restart,and if it fails, locks out. At the lock-out position, the entiremechanism is deenergized. It may be manually reset by a shifting of thecams.

If power falls during the interval of closure of the institutingcircuit,- upon restoration, the starting period continues. If powerfails during the established starting period, upon restoration themechanism operates through the remainder of the starting period, thescavenging period, and starts anew.

If power fails duringthe running period, upon restoration, the mechanismproceeds through the scavenging period, and restarts.

It will be observed that at the end of any operation, normal orabnormal, there is a scaveng ing period prior to restart. This is trueeven after lock-out.

The objects of the invention are to accomplish each and all of the aboveoperations, and to do so with a simple and economical novelconstruction.

A further object of the invention is to provide a control device readilyadapted to secure either continuous or intermittent ignition,

A further object is to provide a cycle of this kind, with or without allof its details, operated with periods of fixed duration.

A further object is to provide in a mechanism of this kind, anignition-responsive device directly controlling the burner motor; and toprovide means to prevent continued operation of the mechanism" and motorif the-said devicefails in either its hot or its cold position.

Further objects include the provision of a cycle means of this kind,insuring a scavenging period after each operation; and to provide acycle having its lock-out occurring prior to the running period.

In the drawings:

Fig. 11s a front elevation of the device mounted on a pipe;

Fig. 2 is a side elevation with the pipe in section;

Fig. 3 is a front elevation with the cover removed;

Fig. 4' is a horizontalsection taken on the line 4-4 at the top of Fig.3;

Fig. 5 is a Vertical section taken on the line 5-5 at the right ofFig.3;

Fig. 6 is a vertical section taken on the line 6-6 of Fig.5; a a

Fig. 7' is a front elevation ,of the casing with all the mechanismremoved except the switch operated by the heat-change responsive device,mounted on the casing;

Fig. 8 is a rear elevation of the partition wall with the mechanismmounted thereon;

Fig. 9 is a section on the line 9-9 of Fig. 4 showing only the front camand its switches;

Fig. 10 is a section on the line lll-l0 of Fig. 4 showing the middle camand its switches;

Fig. 11 is a section on the line I l-H of Fig. 4

' showing the rear cam and its switches;

Fig. 12 is a diagram of the program of the mechanism; and,

Fig. 13 is a general wiring diagram of the mechanism. I V

The mechanism includes an encased unit 40 having a heat-responsivedevice I projecting from the back thereof and supported in a pipe 42 soas to be influenced by heat changes therein. The mechanism 4| is almostinstantly responsive to all changes in heattaking place at or above agiven rate and reversing the heat condition from hot to cold or cold tohot; and it is of the typeshown in co-pending application No. 328,177,filed April 6,1940, PatentNo. 2,323,370, issued July 6, 1943. v

Recapitulating briefly from said applications, the stack unit includesan outer tube and an inner member preferably also a tube. The two mayhave the same coemcient of expansion. The

outer tube is located so as to receive immediately the relativelyunlimited supply of heat if the burner ignites and produces flame, suchas in the furnace stack, and desirably is of thin material so as torespond almost instantly to rapid changes in temperature such as mayoccur in normal starting or stopping of the flame; and it may alsorespond to fluctuations in heat of the flame.

The inner member is exposed at most only at its outer end to the flame,and contains an inner portion connected to a cold reservoir, as theswitch casing and the control casing. The two members are securedtogether toward their outer ends, and preferably the heat from the flamereaches the inner member in its major portion from the outer member.Heat applied to the outer tube causes it to expand. A portion of thisheat is transmitted to the inner tube, but that tube does not expand asmuch, owing to its dissipation of heat into the cold reservoir. Hencetheir will be a relative movement of the inner ends of the memberscausing the snap switch to operate to its closed position. In thestarting position of the tubes, the snap switch is held in anintermediate position, so that it may move in either direction, and staythere under the influence of the snapaction means;

Continued application of heat to the tubes will never bring them to thesame length, owing to the constant dissipation of the limited amolmt ofheat supplied to the inner. Even if the inner tube should heat to apoint of providing approximately the same length differential as at thestart, the switch will not shift, as the starting condition has theswitch floating at a mid-point of the snap-action means. Not until apositive reversal of the length differential occurs can the switch bemoved, by overcoming the force of the snap-action.

If the flame stops, the outer tube will rapidly cool, but the inner tubecannot cool so rapidly. This reverses the length differential, and theouter tube, therefore, displaces the inner, returning the switch to itsfirst position. Continued cooling does not change this, because even inthe initial position the length differential would only put the switchinto neutral position, and the force of the snap-action is ordinarilyadequate to prevent even this.

It will be seen that the device will thus function upon any sudden heatchange reversing the length differential, regardless of the temperature.Normal fluctuations or modulations occur at too slow a rate to cause thefunction. For instance, in a relatively slow decline of heat, the rateof heat dissipation from the outer member is less than the rate of heatdissipation from the inner, or at least is not so much greater a rate asto cause displacement of the end of the inner tube suflicient to movethe switch to a point wherefrom it will snap over.

The uni? itself has a main casing having a rear wah 43, side walls I andjptep wall. and bottom wall ll. The sid walls do not extend forwardly afar as do the top and bottom walls and have inwardly extending flangesupon which is mounted a partition wall ll that provides an inner chamber48. A U-shaped cover flts over the top and bottom walls and back to thesidewalls to enclose a switch chamber.

The mechanism itself includes generally the heat change responsive unit41, a switch 53 operated thereby, the switch being of the type disclosedin copending application, No. 328,177, filed April 6, 1940, having fourterminals. The mechanism also generally includes a control motor ortiming device I, a transformer 55 and a relay N, the last three beingmounted on the back of the partition wall.

The switch 53, as noted, has four terminals. The pair of terminals 81are closed by the switch upon increase of heat applied to the unit II,and the pair of terminals I. are closed upon decrease of heat.

The control motor 54 operates three banks oi control switches that aresupported on the front side of the partition wall II. The motor itselfis mounted on a bracket ll secured to the partition wall. The motor hasa driving gear ll (Fig. 6) that, in turn, drives a gear I! fltted withinan opening in the partition wall. The ratio of these gears determinesthe spread of the cycle, which, therefore, may readily'be changed. Aratchet dog II on the gear 82 is spring-pressed into engagement with aratchet M integral with a hollow cam shaft it that projects through thepartition wall toward the front of the mechanism.

It will be seen that rotation of the gear II in a counterclockwisedirection, in Fig. 6 looking from the back, will cause the gear I torotate in a clockwise direction which, through the medium of theratchet. causes corresponding rotation of the cam shaft 8!. Looking fromthe front, as in Figs. 4 and 9-11, the cams rotate counterclockwise.

The cam shaft supports three cams, a front cam 01, a middle cam II and arear cam 89. The cams are maintained in spaced relation and have anoncircular opening fltting over the noncircular cam shaft 85. A shieldII shields of! the opening through the partition wall 48 in which theear I flts.

Within the hollow cam shaft is a shaft Ii on which is mounted a knob II.This knob is like the one in copending application, No. 328,177, fliedApril 8, 1940, and is designed to permit only a limited movement of theknob. The knob also has a projecting leaf spring 13 at the back thereofthat is adapted to engage at certain times with a button II on the frontcam "I. By this means in a manner the same as described in the mentionedcopending application, the knob 12 may rotate the cams in acounterclockwise direction a distance limited to the permitted movementof the knob II. Release of the knob thereafter allows' it to spring backinto starting position.

The front cam II, as shown in Pig. 9, has a lobe II, a deep notch 84 andan edge ll between the notch M and the lobe II. This cam operates twoswitches II and II. There is a cam follower arm ll having a contact lladapted to close with the contact II on a blade II to constitute switchI. The blade II is limited in its movement by a stop blade I.

A spacer member ll on the arm 0! holds an additional blade 04 spacedfrom the arm I. This blade has a contact II adapted to engage with thecontact 98 on a spring blade 81 which also has a stop blade OI to formswitch :1.

When the follower is on the lobe II, the switch 86 is open, and switch81 is closed. when the cam drops the follower to the edge ll, bothswitches are open, and when it further drops the follower into the notchll, the switch ll closes.

Referring to Fig. 3, it may be seen that all of these several blades aresupported on the partition wall between two brackets "II and Ill. Eachswitch blade carrying a contact is insulated from the others by a seriesof insulating blocks I02, and each blade also extends back of thebrackets and insulating blocks to provide terminal portions to receiveconnections. The several banks of, switches are spaced in accordancewith the spacing of the several cams and all are insulated andconnected, as will be obvious, to obtain the objectives of the wiringdiagram.

The middle cam and its switches are shown in Fig. 10. The cam 68 has alobe I04 from which there extends a somewhat lower lobe I05 followed bya low edge I06, and then a notch I01.

This bank of the switches includes three switches I00, I09 and H0. Thereis a follower arm III'that has a contact I I2 adapted to close with acontact II3 to form the switch I08. The contact II3 is mounted on aswitch blade II4 having a stop blade H5 to limit its movement.

The arm I I I is provided with a spacer member 6 by means of which it isheld in spaced relation to a spring blade II1 having a contact IIO thatis adapted to close with a contact II 9 to form the switch I09. Thecontact H9 is secured to'a spring blade I20 that has a stop blade RI.

The contact H8 has an opposed'contact I22 on the blade lill-thatisadapte to'"clos"with"a2- contact I23 to form the switch II 0. Thecontact I23 is secured to a spring blade I24 which has a stop blade I25.The several blades are mounted between the brackets I and I M and areduly insulated from each'other, as shown.

They are also provided with suitable terminal ends to receiveconnections.

When the cam I04 is in the position shown, the switch I08 is closed andthe switches I09 and H0 are open. When a short time later the cam' liftsthe follower out of the notch I01 onto the edge I06, it opens the switchI08 without closing I09 or IIO. Sometime'thereafter, the edge I liftsthe follower to close the switch I00, and, upon reaching the edge I 06,also closes the switch H0.

The rear cam 69 (Fig. 11) has a lobe I30 followed by an edge I3I that isquit low, and between the edge I3I and the lobe I30 there is amedium-high edge I32. This cam operates switches I33, I34 and I35. Ithas a follower arm I36 with a contact I31 adapted to engage'with acontact I36 to form the switch I33. Thecontact I38 is secured to aswitch blade I30 and there I is a stop blade I40 to limit the movementthereof.

The follower arm I36 also has a second contact I4I adapted to be engagedwith the contact I42 on a blade I43 to form the switch I34. A spacermember I45 holds the blade I43 spaced from another blade I46 that has astop blade I41 to limit its movement. The blade I46 has a contact I40adapted to close with the contact I49 on a blade I50 to form the switchI35. The blade I50 also has a stop blade I5I to limit its movement.

When the position shown in Fig. 11 is attained, the switches I34 and I35 are closed. When the cam rotates so that the follower I36 drops-tothe edge I3I, switches I34 and I 35 will snap open and the switch I33will close. Thereafter, when the cam presents the middle edge I32 to thefol- -lower arm, it opens the switch I33, but does not close theswitches I34 and I35. These two switches are reclosed by the cam lobeI30.

The transformer 55 includes aprimary I60 and a secondary I6I, as shownin the wiring diagram.

The relay 56 includes a coil I62 that, when deenergized, releases anarmature I63 that is biased to close with the contact I64, and to openthe switch I66. When the relay is energized, the.

armature is closed with the contact I65, and the switch166 is closedalso.

The relay coil I62 is in series with the secondary of the transformerand also with the room thermostat I61.

The unit itself on the front of the partition wall has six terminals.The terminals I and "I are adapted to be connected to the leads from theroom or space thermostat. The terminals I12 and I13 are the power lines.From theterminal I14 goes one line to the burner motor, the other lineof which is brought back to the ground power line I13, and from theterminal I goes one lead to the igniter mechanism, the other from whichalso goes to the ground power line I13. The twoground lead lines fromthe igniter and burner motor may, if desired, be connected to theterminal I13. The remaining connections will be clear from theaccompanying wiring diagram.

It will be seen that one terminal 51 of the stack unit is connected tothe switches 81 and I08, and to the terminal I14. The other terminal ofthe switch I03 leads to a bracket I11 (Fig. 5) attached to the partition48, and overlying in spaced relation anextension of'the terminal I 15. Ascrew I18 passes through the extension and is adapted to contact thebracket I11 when tightened, or to be spaced therefrom whenloosened. Thisscrew forms a selective switch I13, and determines whether or not theigniter operates continuously through the running period, or stops atthe end of the first phase of the starting period.

The operation of this cycleis shown in Fig. 12. At the start, the camspresent the several points S to their followers. Reference'to theprogram and to the other figures will show that switches 01, I08, IIO,I33, I34 and I are open, and switches 86 and I03 are closed by theircams,

establishing an instituting circuit through the primary winding I60. Theheat switch 58 is closed because the unit H is cold, and the switch I63isreleased against the contact I64. When the room thermostat switch I61closes, demanding heat, the secondary coil I6I causes the flow ofcurrent through the thermostat switch to the relay coil I62. This closesthe switch I63 against the terminal I 65, and also closes the switchI66. Thereupon, a circuit to the control motor is established from theterminal I12, switch I63, switch I03, through the control motor to theterminal I13. The control motor then begins to operate and to rotate thecams. After about two and a half seconds of operation of the controlmotor, the switches IIO, I34 and I36 close; Closing of the switch I34shunts the switch I63 and holds its circuits independently of the coil-I62 and, hence, of the room thermostat, thus insuring that, for theinterval of closur of the switches I34 and I00,'the control motor willcon- 0 tinue to operate. Also, there is an additional holding circuitfor the primary I of the transformer which is independent of theswitches 86 and 50, and which includes either the switch I34 or theswitch I63, the switch I09, the switch I35, the switch I66 and theprimary I60.

Closing of the switch IIO puts the ignition device in circuit directlyin parallel with the control motor. The igniter thereupon begins tooperate. After the lapse of about twelve and 70 one-half seconds theswitch 06 opens and the I switch 01 closes. Opening of the switch 86 hasno eiiect at this time. because of the previously established'holdingcircuitto the coil I60 through the switch I 35. It does preventreclosing of the primary circuit upon lock-out or after the runhingperiod, and thereby insures that the switch I63 will remain againstcontact I to insure the scavenging period, as will be seen. Closing ofthe switch 81 establishes the circuit to the bumer motor which includeseither the switch I or the switch I63, the switch I", the switch I, theswitch 81 and the burner motor. When the burner motor starts, fuel issupplied and in due course will be ignited by the igniter. It is to beobserved that the lgnlter is operated prior to the burner motor, adesirable safety feature.

When the ignition takes place, the stack switch operates almostinstantly so that the switch 51 is closed and the switch 58 is opened.This then establishes a circuit to the burner motor by way of either theswitch III or the switch I", and the switch 51. It also establishes anadditional circuit to the coil I from the switch I1 and through theswitch 01 and the switch I. It likewise establishes an additionalcircuit to the control motor from the switch 1, the switch 8'! and theswitch I, and additionally establishes a circuit to the igniter throughthe switch IIO.

After the lapse oi a period of sixty seconds, the first phase of thestarting period, the switches I and H0 open and the switch I" closes.Opening of the switch Ill breaks its circuit to the control motor, butthat motor continues because oi. the alternative circuit through theswitch 51. This circuit holds the coil I60 through the switches 81 andI, the control motor through the switches 81 and I35, ignition devicethrough switch IIII, and the burner motor. Thereupon, the continuedholding of the circuits depends upon the continued flame to hold thestack switch 51 closed.

Thus, continued operation of the normal cycle depends upon the conditionat the end of sixty seconds. If normal ignition takes place. themechanism will continue for an additional ten seconds interval. untilthe lapse of seventy seconds, at which time the switches I and III willopen and the switch I" will close. This interval is th second phase ofthe starting period. It is a lock-out period. Closing oi! the switch inhas no effect as long as the switch IE3 is closed against the contactI". Opening of the switch I34 leaves the circuit dependent upon theposition of the switch I" and. therefore, upon the condition of the roomthermostat. Opening of the switch I" has no effect on the coil I" aslong as flame continues, because of the alternate circuit to the coilthrough the switches 51, I1 and I". It does, however, have an eflect onthe condition of the control motor which was previously in circuit onlythrough the switch I35. This m'otor, therefore, stops. The ignitiondevice remains in circuit through the switches 51, I" and I1! if thelatter is closed. For some burners this is a desirable safety feature.For others, it is not necessary, and so, upon loosening the screw I'llto open the switch I19, the efiect of the switch I" in holding theigniter in circuit is nullified, and it ceases operation upon opening ofthe switch III at the end of sixty seconds. The switch I" is held closedfor a short time beyond the seventy-second point to insure operation ofthe igniter even when the control motor floats or coasts for an intervalafter deenergization. V

when the control motor stops, the mechanism is in the operating orrunning stage, and is wholly dependent for continuance of this stageupon continusdclosureoitheroomthermostaathestsck switch II, and therelay switch III. of course, the'timing motor switch Tl must remainclosed.

As soon as the room thermostat is satisfied and opens, the coil I" isdeenergized, the switch I" shifts to the contact I, and the switch I"opens. The fact that the instituting circuit is broken at the switch Itprevents energization of the primary at this point, so that th switch Ican shift. This cuts the primary I" out oi circuit. It cuts the burnermotor out oi circuit because it breaks the line to the switch '1. Itcuts the ignition device out oi circuit for the same reason. However,closing the switch Ill with the contact I, with the closure of theswitch III, establishes a circuit through those two switches to thecontrol motor which again begins to operate.

Very promptly (preferably and normally a matter of seconds) alter theburner motor stops, the heat will dropai; the stack unit II at a greatrate so that the switch a closes and the switch 51 opens. Thishas noeflect on the established circuits.

After the lapse of flve more seconds or, disregarding the runningperiod, seventy-live seconds from the start, the switch I opens. Thishas no immediate eiiect. Continuing the switch Ill beyond theseventy-second point assuresoperation of the igniter, despite thefloating or coasting interval of the control motor. This, of course,assumes that the switch I'll is closed. Alter the lapse of eightyseconds, the switch 01 opens with no immediate eflect. The switch IIlikewise accommodates the coasting period.

The control motor alone will continue to operate until almost the end orthe entire cycle, which cycle is here shown at 240 seconds. This insuresalong scavenging period to take care oi! allunburned fuel.

Alter the lapse of 230 seconds. the switch Ill again closes. This has noeiiect. because the switch I is closed against the contact Ill andbecause even any circuit established through the switches III and I isbroken at the switch II, and any circuit to the switch I] is broken atswitch I34.

Thereafter, at 235 seconds, the swtich ll closes again to reestablish acircuit to the primary I. The primary, however, is inactive because theroom thermostat is open. No other circuits are established by this act.

At the end of 240 seconds, the switch I opens again and thereby allcircuits other than the instituting circuit to the coil I open. Thecontrol motor stops and the mechanism awaits a new call by the roomthermostat.

It has previously been noted that, alter a sixty-second interval, thecircuit is dependent upon ignition, because it is dependent upon thecondition of the switch 51, which closes only upon the existence ofignition at the sixty-second point. If it be assumed that ignition doesnot exist at this time and that the switch I is open, the mechanism willstop after this lapse of sixty seconds. Thisis the look-out position.

At this lock-out position, the button ll on the front cam 01 has lustpassed under and is in front of the leai spring 13 on the knob I2. Themechanism can be reoperated only by manual rotation 0! this knobcounterclockwise as far as it will go, here about 45 It then may bereleased, and will automatically return to its first position afterhaving displaced the cams.

At the time the mechanism stops, prior to turning the knob, the switchesII, I, I", III and 81 are closed and switches 51, 88, I33, I86 and I IIIare open. The switches occupy these positions in Figs. 9, and 11. Allcircuits, including those to the primary I68, are open.

Rotation of the knob shifts the cam 61 until 5 the lobe 83 is removedfrom the follower 88, which rests upon the edge 85. In this position,switches 86 and 81 are both open. Rotation shifts the cam 68 beyond thenotch I01 until the follower III rides on the edge I66, in whichposition all of its switches I08, I68 and III! are open. Rotation alsoshifts the cam 63 until its follower I36 falls onto the edge I3I, inwhich switch I33 is closed, switches I34 and I35 open.

Thus, rotation of the knob advances the mechanism to a short distancebeyond the start of the scavenging period, skipping the intermediateperiod and running period. The control motor is in circuit, andcompletes its cycle. Here, again, the fact that the switch 81 is openprevents operation of the relay, and enables the scavenging is to occur.If the room thermostat demands at the end of the cycle, the mechanismwill start over again.

In case of flame failure during the running period, occasioned by breakof fuel supply or any familiar cause, the igniter being in circuit willnormally restart the flame before the failure is eff ctive on the stackswitch. If the stack switch cools to open the switch and close theswitch during the runningperiod, as switch 86 is, open, the primary willbe deenergized, the switch I 63 will close with contact I64, thescavenging period will occur and the mechanism will return startingposition where it will be under control oi the room thermostat. If thethermostat continuesto demand heat, a new cycle will begin. If flame.failure was due to some cause that prevents ignition in the new cycle,the mechanism will pass to the lock-out position.

In case of power failure and restoration dur ing the first twelve andone-half seconds during which the switch 86 and the instituting circuitare closed, the mechanism will take up where it left off. Upon powerfailure between twelve and one-half and sixty seconds, the coils I60 andI6I i will be deenergized, opening the switch I66, and

shifting the switch I63 to the contact I 64.

Restoration of power will produce circuits around the switch I63,through switch I34, but the coils will not be reenergized because theswitch I66 is open. The control motor will run, through switches I34 andI89, the ignition device through switch III), and the burner motorthrough switches I35 and 81., when the sixty point is reached, theswitch I69 opens, but if ignition has occurred, the switch 51 hasclosed, and the burner motor continues through switches I34 and 51, withthe control motor continuing through switches I34, 51, 81 and I35, andthe nition device through switches I34, 51 and new- 1y closed switchI88. The cycle will continue to theseventmsecond interval, the normalstart of the running period. At this point, switches I34 and I35 open.This breaks the circuit to the burner motor, because the switch I63 isclosed with contact I84. However, at this time, the switch I33 hasciosed, so that the normal scavenging period is established, and themechanism will complete it and restart, if the thermostat demands. Itthus may be said that the power condition at twelve and one-half secondspredetermines what will happen at seventy seconds, viz., whether therunning period will occur or not.

If power fails and is restored during the inposite positions.

termediate interval between sixty and seventy seconds, the coils I andI6I will be deenerize'd, switch I63 shifts to contact I64, and switchI66 opens. As the switch I33 is open at this time, lock-out will result,unless the power failure occurred so near the end of the intermediateperiod that the control motor coasted to a point closing the switch I33,and thereupon setting the mechanism for a scavenging operation uponpower restoration.

If power fails and is restored during the running period, the coils willbe deenergized, the switch I63 shifted to the contact I 64, and thescavenging eriod started at once, returning the mechanism to startingposition.

If power fails and is restored during the scavenging period, themechanism will take u where it left off, By considering the wiringdiagram, it may be seen that the switch 86; when closed, permits theinstituting circuit to be closed. The switch opens prior to lock-out torender the look-out effective, since otherwise the circuit to theprimary would not be broken by opening of the switchfIIliI, and thecontrol motor, ignition and burner motor could continue by circuitsthrough switches 86, 58, I66, either I35 or 81, with I08 and III). Theswitch 86 opens also to render th mechanism subject to power failure.

The switch 58 has the function of preventing recycling if the switch 51fails in hot position, because the switch 58, under such circumstances,will be. open, prohibiting closing of the in'stitutin circuit, the twoswitches being mechanically disposed to be operated by'the switch bladein cp- If the switch fails cold, the instituting circuit will be broken,as noted, by the switch 86, and lock-out will occur.

The switch- I34, as noted, insures a starting cycle up to lock-out oncethe control motor has operated to close it, regardless of the conditionof the room thermostat. If ignition does not take place-prior to openingof the switch I08. lockout will occur. If ignition does occur, then theopening of the room thermostat will release the switch I63 to contactI65, and will open the switch I66, but the burner motor will remain incircuit through the switch 51, the control motor through 51, 81 and I35,until the switch I34 opens, and the switch I33 simultaneously closes,establishing the scavenging period. -Hence, operation of the roomthermostat during any phase of the starting period does not disrupt thenormal cycle. s,

The switch I 63 is a selector switch, determining whether the scavengingor operating circuits of the control motor shall function. It, ofcourse, interlocks its circuits with the room thermostat. and theselection it makes is dependent upon the room thermostat. Likewise, itselects in response to heme failure, when it is dependent upon theswitch 51 for its position, and it selects in response to power failure,when it is dependent upon the switch I86. Its holding circuit, being attimes dependent upon flame switch 51, power failure switch I66, and theroom thermostat I61, its selection depends upon the conditions of theseswitches.

The switch I66 is the power failure switch. As it controls the holdingcircuit for the room thermostat and the selector switch, it controls theentire mechanism for power failure. It is ineffective only when theinstituting circuit is closed.

The switch I33 controls the scavenging opera,-

tion. Upon failure of ignition, with lock-out,

the selector switch droos over to scavenging position. If the switch I38were not present, lock-- out could not occur. as the scavenging cyclewould' start forthwith. Thus, the switch I" spaces the start ofscavenging from the point of lock-out.

The switch I is the look-out switch. When mentioned manner of renderingthe lock-out circuit efiective.

The switches liil and Ill, thelatter with the switclfllfi, controloperation of the igniter.

The switch 81 has two primary functions. If it were not present, theinitial burner motor circuit would be closed upon closure of the switchI, prior to energizing the igniter, an obvious disadvantage. Also, if itwere not present, there would be a burner motor circuit immediately uponclosing of the room thermostat and the switch i", through 8', 58, I",the circuit across I1 and the burner motor. The switch l'l must be openduring the effective period of the instituting circuit and until it isdesired to energize the burner motor; it must be closed to operate theenergizing circuit; and it must be closed durin the second phase of thestarting period and during the running period to close the holdingcircuit for the selector switch, the power failure switch and the roomthermostat circuit.

The switch I is clearly a fiarne safety switch. Its being in series withthe power failure relay holding switch causes it to control the entiremechanism, and when opened to effect deenergization of the entiremechanism, unless a proper recyclingoccurs. If it fails cold, lock-outresults; if it fails hot, no starting can occur, as above noted inconnection with its companion switch ll.

It will be seen that no separate power failure relay is here required,owing to the connections making the main relay into a power failurerelay. The resistor shown controls the amount of current in thetransformer and thermostat circuit.

In the foregoing, the object has not been to explain every function ofeach switch and each circuit, but rather to elucidate some of thepurposes of the several parts. It may be noted, for instance, that theuse of a choke coil and separate thermostat circuit to short circuit itas well as to receive a utilitarian current could be replaced by adirect connection of the thermostat and the relay coil. Other likesubstitutiom could be made within the scope of the appended claims.

What is claimed is:

1. Inamechanismofthekinddescribed,afuel supply device, a thermostat, acircuit for the thermostat, a first switch in said circuit, a circuitfor the supply device, including means connecting the supply devicecircuit into the thermostat circuit after the first switch, anddependent upon continued power to hold the thermostat circuit throughsaid connection independently of the first switch, timing means to openthe first switch and to close the fuel supply device circuit at the sametime, and means to start operation of the timing means upon closure ofthe thermostat circuit.

2. In a mechanism of the kind described, a fuel supply device, a timingdevice having a plurality of cam switches for producing a completecycling operation of the fuel supply device, means including a camoperated switch adapted to be opened to stop operation of the timingdevice short of the end of the cycle, and means to displace thecamswitchestocauserestartingofthetiming device.

3.Inamechanismofthekinddescribed,a burner, a fuel supply device, acontrol means for the fuel supply device to provide a first periodduring which ignition may ordinarily occur and a running period for theburner, a power failure relay including a relay switch, means to causeenergization of the relay to effect closure of the relay switch, acircuit through the relay switch for starting the control means, a shuntcircuit closed by the control device after its operation has begun, tomaintain the control device in operation for the first periodindependent of the relay, and means to prevent reenergiaation of therelay upon failure of power during the said first period, independent ofthe existence or lack of combustion.

4.'Ina mechanism ofthe kind described, a burner, a fuel supply device, afirst control for the fuel supply device adapted for movement to openand closed positions, a second control means for the fuel s pply deviceadapted to provide a first period during which ignition may normallyoccur, and a running period thereafter, a circuit for the second controlmeans adapted to be closed upon closure of the first control means,means operated by the second control means to maintainthesecondcontroimeansinoperationfor said first period regardless of opening ofsaid first control during said first period, and means to prevent theexistence of the running period if the first control is opened duringsaid first period during operation of said maintaining means.

5. In a mechanism of the kind described. a fuel supply means. a firstcontrol therefor, a second control adapted to provide a first period ofoperation' of the fuel supply means during which ignition may occur. anda running period thereafter, said first control being operable to twopositions, a first circuit for the second control through the firstcontrol in its first position. and a second circuit for the secondcontrol through the first control in second position, means to operatethe first control to second position to cause operation of the secondcontrol through said second circuit, means operated by the secondcontrol means to maintain said second control in operation for the firstperiod regardless of the position of the first control, and meansmaintaining said second control in operation after said first periodthrough said first circuit, whaisaidfirstcontrolisinitsfirstpositionattheend of said first period.

6. Inamechanismof the kind described, afnel supply means, a firstcontrol therefor a relay and a relay switch. the switch being actuatedfrom a first position when the relay is deenergized to a second positionwhen it is energized. thermostatic means operable to cause energizationof the relay only when a predetermined temperature condition is reached,a second control adapted to provide sequentially a first period ofoperation of the fuel supply meansduringwhichignitionmayoccuhandarunning a second circuit for the secondcontrol through the first control in first position, and saidmaintaining means being adapted to render the second control subject tocontinued operation through the relay swith in first position at the endof said first period when said relay switch has returned to its firstposition.

7. In a mechanism of the kind described, a burner, a fuel supply devicetherefor, a control means to provide a first period during whichignition may occur, and a running period for the burner, a power failurerelay including a relay switch, means to cause energization of the relayto effect closure of the relay switch, a circuit through the relayswitch for starting the control device, a circuit for starting the fuelsupply device, means to maintain the control device and the fuel supplvdevice in operation for the said first period independent of the relay,and means to prevent continued operation of the fuel supply deviceafter'said period upon failure of power and release of the relay duringsaid period. j

8. In a mechanism of the kind described, a burner, a fuel supply devicetherefor, a. control means to provide a first period during whichignition may occur, and a running period for the burner, a power failurerelay including a relay switch, means to cause energizatlon of the relayto effect closure of the relay switch, a circuit through the relayswitch for starting the control device, a circuit for starting the fuelsupply device, means to maintain the control device and the fuel'supplydevice in operation for the said first period independent of the relay,an additional circuit for the fuel supply means dependent upon theenergization of the relay, the opening of said maintainingmeans'rendering the fuel supply means dependent upon said additionalcircuit, and means to prevent reenergizatlon of the relay once ithas'been released. I

9. In a mechanism of the kind described, a burner, a fuel supplydevice'therefor, a control means toprovide a first period during whichignition may occur, and a running periodfor the burner, a power failurerelay including a relay switch, means to'cause energization of the relayto effect closure of the relay switch, a circuit through the relayswitch for starting the control device, a circuit for starting the fuelsupply device, means to maintain the control device and the fuel supplydevice in operation for the said first period independent of the relay,an addi- 10. In a mechansim of the kind described, a

burner, a fuel supply means therefor, a power failure means, a control"mechanism adapted to provide a first period for the burner during whichI ignition may occur, an intermediatepe'riod, and a running period,means to cause starting of the fuel supply means during the firstperiod, means dependent upon existence of conibustion to maintainthefuel supplymeans in operation for the intermediate period, and meansdependent upon combustion for maintaining the fuel supply means inoperation for the running period, means to maintain the controlmechanism in operation for the first period independently of the powerfailure moans, means to maintain the control mechanism in operation forthe intermediate period independently of the power failure, means butdependent upon combustion, and means to stop the fuel supply means butto maintain the control mechanism in operation after the intermediateperiod upon failure of power during the first period. I

11. In a mechanism of the kind described, a fuel supply means to supplyfuel to be ignited, control means to provide sequentially a startingperiod during which combustion may occur, and

'a running period, automatic means to start the means responsive toexistence of combustion to maintainsaid fuel supply means in operation,

power failure means adapted to render the fuel supply means inoperative,and means to continue operation of the fuelsupply means for additionaltime upon failure of power for an interval too short to cause the meansresponsive to combustion to'renderthe fuel supply means inoperative.

13. In a mechanism of the kind described, a fuel supply device, acontrol mechanism adapted to provide sequential operations for the fuelsupply device, a combustion-responsive device closed upon existence ofcombustion, means to effect starting of the control mechanism, circuitmeans through the combustion responsive device including a branch forthe control mechanism and a branch for the fuel supply device, means inthe control mechanism to render the control mechanism and fuel supplydevice dependent upon said circuit means, means in the control mechanismbranch operated by the control mechanism to render the control mechanisminoperative, a power-responsive means having a switch controlling saidcircuit'meanaand a coil, said circuit means having a third branchproviding a coil energizing means, and means under control of thecontrol mechanism to maintain said third branch closed when the controlmechanism branch is opened, and an additional circuit to the controlmeans adapted to be closed through the powerresponsive means switch whenthe coil is deenergized. I

14. In a mechanism of the kind described, a burner, acombustion-responsive means operable to hot or cold positions, means tocause the burner to operate for a running period dependent upon thecombustion-responsive means, means providing a, scavenging period afterthe running period, said scavenging period means being adapted tooperate after ,a running, period whether or not thecombustion-responsive 'means operates to hot or cold position, means toprevent re-establishment of operation of the burner unless thecombustion-responsive means is in cold position, and means to insurecapacity to recycle if the combustion-responsive means is in coldposition;

15. In a mechanism of the kind described, a burner, a relay switch, acombustion-responsive switch, a control mechanism, means to operate thecontrol mechanism to provide sequential operation of the burner, acircuit for the burner including the relay switch and thecombustionresponsive switch in series, whereby when either switch failsto function the burner may nevertheless be controlled by the other, andmeans to prevent restarting of the control mechanism upon failure of therelay switch and opening of the combustion-responsive switch.

16. In a mechanism of the kind described, a burner, a first controlswitch responsive to predetermined conditions, a combustion-responsiveswitch, a control mechanism including a plurality of sequentiallyoperated switches, a first circuit including a control mechanism switchto maintain the control mechanism in operation for a predeterminedinterval, a second circuit means including the combustion-responsiveswitch to maintain the control mechanism and the burner in operation foran additional period, and a third circuit including thecombustion-responsive switch and the first control switch in series tomaintain the burner but not the control mechanism in operation aftersaid additional period, whereby upon failure of either thecombustionresponsive switch or the first control switch to open, theburner remains under control of the other switch.

17. In a mechanism of the kind described, a control device, a fuelsupply device, a first switch, a second switch, said control devicebeing adapted to maintain the first switch open when the second isclosed, a first circuit including a branch to the control device and abranch to the fuel supply device, means to control said first circuit,to control both devices, said first switch being in the fuel supplydevice branch, and a second circuit for the control device includingsaid second switch, whereby when the first switch is closed both devicesmay be energized through the first circuit, and when the first switch isopen and the second closed, the control device may operate withoutoperation of the fuel supply device.

18. In a mechanism of the kind described, a

control device, a fuel supply device, a first switch, a second switch,an ignition-responsive switch, said control device being adapted tomaintain. the first switch open when the second is closed, a firstcircuit including a branch to the control device and a branch to thefuel supply device, means to control said first circuit to control bothdevices, said fuel supply device branch including said first switchwhereby both devices may be operated through said first circuit when thefirst switch is closed, a second circuit to the fuel supply deviceincluding said combustion-responsive switch, whereby both devices mayoperate together through said second circuit when saidignition-responsive switch and first switch are closed, and whereby uponopening of the first switch said fuel supply device alone may beoperated through the second circuit, and a third circuit for the controldevice including said second switch but not said first switch, wherebywhen the second switch is closed and the first open, the control devicemay be operated without the fuel supply device, and means to select thefirst or the third circuit.

19. In a mechanism of the kind described, a control device, a firstcircuit adapted to institute operation of the control device, a secondcircuit adapted to continue operation of the control device, a.connection between the circuits and dividing the first circuit into twoparts, means operated through the second part of the first circuit tocontrol the closure of the second circuit, a first 16 switch in thefirst part of the first circuit, and a second switch in the secondcircuit, said second switch being adapted to be opened to break thesecond circuit, and means opening the first switch as early as thesecond switch is opened.

20. In a'mechanism of the kind described. a control device, a firstcircuit adapted to institute operation of the control device, a secondcircuit adapted to continue operation of the control device, aconnection between the circuits and dividing the first circuit into twoparts, means operated through the second part of the first circuit tocontrol closure of the second circuit, a first switch in the first partof the first circuit, and a second switch in the second circuit, saidsecond switch being adapted to be opened to break the second circuit,and means opening the first switch as early as the second switch isopened, together with a fuel supply means, and a connection between thefuel supply means and the second circuit to cause operation of the fuelsupply means when the second circuit is closed.

21. In a mechanism of the kind described, a control device, a firstcircuit adapted to institute operation of the control device, a secondcircuit adapted to continue operation of the control device, aconnection between the circuits and dividing the first circuit into twoparts, means operated through the second part of the first circuit tocontrol closure of the second circuit, a first switch in the first partof the first circuit, and a second switch in the second circuit, saidsecond switch being adapted to be opened to break the second circuit,and means opening the first switch as early as the second switch isopened, together with a fuel supply means, a connection between the fuelsupply means and both the first and second circuits, switch means insaid lastnamed connection, and means to maintain said last-named switchmeans open during closure of the first circuit.

22. In a mechanism of the kind described. a control device, a firstcircuit adapted to institute operation of the control device, a secondcircuit adapted to continue operation of the control device, aconnection between the circuits and dividing the first circuit into twoparts, means operated through the second part of the first circuit tocontrol closure of the second circuit, a first switch in the first partof the first circuit, and a second switch in the second circuit, saidsecond switch being adapted to be opened to break the second circuit,and means opening the first switch as early as the second switch isopened, together with a fuel supply means, a connection between the fuelsupply means and the second circuit to render the fuel supply meansdependent upon the second switch, a third circuit means dependent uponcombustion to maintain the fuel supply means in operation upon openingof the second circuit, a switch means in the last-named connectionbetween the third and second circuits, and means to maintain saidlast-named switch means open when the first circuit is closed.

23. In a mechanism of the kind described, a control device, a firstcircuit adapted to institute operation of the control device, a secondcircuit adapted to continue operation of the control device, aconnection between the circuits and dividing the first circuit into twoparts, means operated through the second part of the first circuittocontrol closure of the second circuit, a first switch in the firstpart of the first circuit, and a second switch in the second circuit,said second r 17' switch being adapted to be opened to break the secondcircuit, and means opening the first switch as early as the secondswitch is opened, together with a fuel supply means, a connectionbetween the fuel supply means and the second circuit to render the fuelsupply means dependent upon the second switch, a third circuit meansdependent upon ignition to maintain the fuel supply means in operationupon opening of the second circuit, a switch means in the last-namedconnection between the third and second circuits, and means to maintainsaid last-named switch means open when the first circuit is closed, saidthird circuit including a switch means dependent upon the existence ofcombustion to be closed.

the control means switch, the combustion-responsive switch, and the fuelsupply device, a connection leading from the second circuit after thecombustion-responsive switch to the timing means, said connectionincluding the second timing means switch, said timing means beingadapted to have its first switch to be closed at the start of a cycleand to open a, time interval thereafter, and being adapted to close itssecond switch before opening of its first switch, and to open itla timeinterval after opening of the first timing means switch, plus a thirdtiming means switch and connections including the same to 24. In amechanism of the kind described, an

operated device, a control mechanism including a plurality of switches,said control mechanism being adapted to operate the switchesequentially, circuit means including said switches, and adapted toprovide sequentially a starting period, a lock-cut, an intermediateperiod, and a return period, for the operated device. said switchesbeing bodily displaceable independently of operation of the controlmechanism, and means to displace the switches from lock-out position toreturn position.

25. In a mechanism of the kind described, a control mechanism having aplurality of sequentially operated switches, and means for operating thesame, a fuel supply device, means including at least one of saidswitches to provide a starting period for the fuel supply device, meansincluding at least one of said switches to provide a look-out for saiddevice, means including at least one of said switches to cause saidcontrol mechanism to restart after said lock-out, said switch operatingmeans being displaceable independently of operation of the controlmechanism, and means to displace said switch operating shunt the controlmeans, said timing means being adapted to close said third switch afterthe timing means has started, and to open the same after a predeterminedinterval during which combustion may occur.

28. In a control mechanism, a control means operable in response topredetermined conditions, including a, switch, a fuel supply device, atiming means, a first timing means switch, a second timing means switch,a combustion-responsive switch, a first circuit to the timing meansincluding the control means switch, the first timing means switch, andthe timing means, a second circuit for the fuel supply device includingthe control means switch, the combustion-responsive switch, and the fuelsupply device, a connection leading from the second circuit after thecombustion-responsive switch to the timing means, said means independentof the control mechanism tion-responsive switch to the timing means,said connection including the second timing means switch. said timingmeans being adapted to have its first switch to be closed at the startof a cycle and to open a time interval thereafter, and being adapted toclose its second switch before opening of its first switch, and to openit a time interval after opening of the first timing means switch.

2'1. In a control mechanism, a control means operable in res onse topredetermined conditions, including a switch. a fuel supply device, atiming means, a first timing means switch, a. second timing meansswitch, a combustion-responsive switch, a first circuit to the timingmeans including the control means switch, the first timin: means switch.and the timing'means. a. secand circuit for the fuel supply deviceincluding connection including the second timing means switch, saidtiming means being adapted to have its first switch to be closed at thestart of a cycle and to open a time interval thereaftenand being adaptedto close its second switch before opening of its first switch, and toopen it a time interval after opening of the first timing means switch,plus a scavenging timing means switch, and connections including thesame, said connections including the (control means switch ininoperative position, and the timing means, said timing means beingadapted to close said scavenging switch after the timing means hasstarted, and to maintain it closed for a predetermined time after thesecond timing means switch has opened, until the timing means returns toits starting condition.

GEORGE D. BOWER.

REFERENCES crrEn The following references are of record in the file ofthis patent:

UNITED STATES PATENTS Number Name Date 1.877037 Parker Sept. 13, 19322.139504 King Dec. 6, 1938 2,085 577 Eaton June 29, 1937 1,888,602Macrae et a1 Nov. 22, 1932 2,078,109 Townsend Apr. 20, 1937 I 1,732,174Sweatt Oct. 15, 1929 1,883,242 Bogle Oct. 18, 1932 2021,647 DeLanceyNov. 19, 1935 1,991.185 Williams Feb. 12, 1935 1,774,137 Good at al Aug.26, 1930 2,160,592 King May 30, 1939 FOREIGN PATENTS Number Country Date173,006 Swiss Nov. 15, 1934

